The invention is apparatus for the testing of motor vehicles comprising a movable endless simulated road surface (such as an endless belt) for cooperation with a motor vehicle restrained from longitudinal movement relative to the direction of motion of the simulated road surface. The four wheels of the motor vehicle, when the apparatus is operational, are in contact with the peripheral road-simulating surface. Operation is possible in one of two ways: Either the motor vehicle engine is operated, the motor vehicle put in gear and the motor driven, thereby forcing the endless road surface to move relative to the fixed motor vehicle, or else the motor vehicle transmission is put in neutral and the endless simulated road surface is separately driven.
The general concept of providing a test bed with a movable surface to support a pair of wheels of a motor vehicle is well known. An example of such a test bed is described in U.S. Pat. No. 4,158,961 (Ben-David, June 26, 1979). The Ben-David apparatus comprises a pair of rollers between which may be rotated a pair of wheels of a motor vehicle. There is no provision for similar support of any of the other wheels of the motor vehicle. The small rollers in contact with the motor vehicle's wheel supported do not really purport to simulate a road surface--they are too small in diameter to make this possible. Even if the Ben-David apparatus were duplicated so that another pair of the motor vehicle wheels were supported, this would still not provide a road surface simulation, because quite artificially the two pair of motor vehicle support wheels would be in contact with and separately engaging completely different sets of rotating support surfaces. This does not serve to simulate a road surface at all--in a road surface simulation test, obviously the dynamics of the entire motor vehicle relative to the road should should be evaluated if at all possible.
Heretofore the most common method of testing motor vehicles for driving and handling characteristics and the like on a road has been accomplished by driving the motor vehicle on a test track. This kind of testing will still continue to be required, since test conditions involving loose sand, slalom courses, etc., cannot readily be provided by a stationary testing facility. However, the disadvantages of test track monitoring are obvious--it is frequently impossible to obtain dynamic measurements of the motor vehicle under operating conditions, difficult to produce acceptable motion picture or video taped records of motor vehicle dynamics, etc. This is presumably what led to Ben-David's proposal that some of these dynamic characteristics be investigated by keeping the motor vehicle stationary whilst permitting a pair of its wheels to engage rotatable rollers thereby to permit some observation of the dynamics of the pair of wheels under test.
Ben-David also recognized that for some purposes it may be desirable to have the inertial mass of the roller system in contact with the motor vehicle wheels under test to be roughly equal to the mass of the motor vehicle. He proposed in the aforementioned U.S. patent that a flywheel be attached to one of the rollers so as to simulate the vehicle weight. However, apart from the fundamental problem with his proposal indicated previously, namely, the incapability of his device to simulate an actual road surface, there are these additional disadvantages associated with the Ben-David proposal:
1. There is no disclosure of any means for adjusting the inertial mass of the system to enable testing of a multiplicity of motor vehicles of varying masses.
2. There is no possibility of steering the motor vehicle relative to the movable support surface.
3. There is no means provided for varying the texture or profile of the support for the motor vehicle wheels.
4. There is no means for simulating other dynamic conditions which may be encountered by a motor vehicle in actual use, such as wind resistance.